Induction motor control



Feb. 29, 1944. A. o. GRooMs 2,342,658

I INDUCTION MOTOR CONTROL Filed Nov. so, 1940 4 sheets-sheet 1 I Illas INVENTOR.

A. O. GROOMS INDUCTION MOTOR CONTROL Feb. 29, 1944.

4 Sheets-Sheet 2 y Filed Nov. 30. 1940 BY E E 0 INVENTOR.

Feb; 29, 1944'. A, Q GROOMS 2,342,658

INDUCTION MOTOR CONTROL Filed Nov. so, 1940 4 sheets-sheet 5 -H H I?. 9 J/7 /Q 4/01 5. 9| 545 13 7 l/l I 3 /0 565 56] 585 367 J ul i 363 INlLLT 54 555 l 5v 595 557 `,59.3 c@ 7 f/ 4@ 7 A 1N VENTOR. o o Ooo BY l l ATTORNEYS Feb. 29, 1944. A o, GROOMS A 2,342,658

INDUCTION MOTOR CONTROL Filed Nov. so, 1940 4 sheets-sheet 4 9o H T 579 577-f /faas x :fz/ l E Z aol Ja 4/ if 55 v 559 54 /r? Ja/ aaa f lNLUeATON Je I a M7 wa/g 565 56 5 v3.65 Je# ,9 /m 567 U 565 J V (IV 57:5 @s am l, 5f .55.9 5691 575 9 557 5674,

M0 INVENTOR.

ATTORNEYS Y IZ-II tif-Fig. 8.

Patented Feb. 29, 1944 lwnUc'rIoN Moron coN'rnoL 'i l Albert Grooms. Dayton. ohio, assigner toGeni eral Motors Corporation. Dayton, Ohm-acorporation of Delaware Application November so. w40, serial No. :sasso (ci. riz-279) This invention relates to temperature and motor controls.

It is an object of my invention to provide a temperature and motor control in one unit, which is so constructed that each feature of the control is provided with an independent adjustment.

It is another object of my invention to provide a combined temperature and automatic overload control in which only one contactmechanism is used.

It is another object of my invention'to provide a simple relay with a simple timing device for opening the relay.

It is another object of my invention to provide a rivet or fastening member of plastic electrical insulating material.

It is still another object of my invention to provide a control incorporating separate bimetals for operating the starting and overload controls for an electric motor.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a view of a unitary temperature and motor control together with a diagrammatic refrigerating system;

o Fig. 2 is a fragmentary view of a portion lo' cated in the rear of Fig. 1, taken on the line 2-2 0f Fig. 4; o

Fig. 3 is a fragmentary view showing a modification of `a portion of Fig. 1;

Fig. 4 is a sectional view taken along the line l-l of Fis. l;

Fig. 5 is a view of a modified form of relay together with an electric motor; shown diagram-4 matically;

Fig. 6 is a view of another type of combined temperature and motor control together with a diagrammatic illustration of an electric motor;

Fig. 'I is a sectional view taken along the line 1--1 or Fig. 6; l

Fig. 8 isl a view cfa portionof Fig. 8 showing the switch in the open circuit position;

Fig. 9 is a sectional view taken along the lines 'l-l of Fig. 6;

Fig. 10 is a sectional view taken along the line i-II of Fig. 6:

Fig. 1l is a sectional view taken along the line H-II ofFig.6; and

Fig. 12 is a sectional view taken along the line ,v Briefly. I have shown a unitary refrigerator including an electromagnetic motor starting control, a current-operated bimetal overload control and a pressure-operated snapacting thermostat control which operates the overload control in order to start and stop the system. In one modied form 'a plastic rivet of electrical insulating material is used to prevent arcing where the rivet is near other metal parts. In still another modification an electromagnetic relay is provided with a bimetal contact arm which becomes heated when the relay is energized to open the relay so as to prevent the relay from being energized too long under certain conditions. In still another modiiled form both the motor starting and overload controls are of the bimetal type and these are also operated by a pressure-operated means to normally start and stop the system.

Referring now to the drawings and more particularly to Figs. 1, 2 and 4. there is shown a reyfrigerating system including a sealed motorcompressor unit 20 including a driving motor 22 having a main winding 2l and starting winding 2i for operating the compressor 28. The compressor 28 withdraws evaporatedv refrigerant from the evaporating means Il located in the compartment 32 to be cooled. This evaporated refrigerant is then compressed and forwarded to the condenser 84 where it is liquefied and returned to the evaporator under a suitable control such as a restrlctor 36. In order to properly control the operation of the refrigerating system,

a thermostat is normally provided.

In this'system, the thermostat includes a thermostat bulb 3l mounted in heat'exchange relation with the evaporating means III and connected by tubing lo to a bellows 42 which is mounted y in the metal frame I4. This bellows 42 operates control for a 56 a primary lever Il which in turn is connected to a toggle mechanism including a secondary lever It, a toggle spring 5l and a third lever 52 which is pivoted upon the pin 54.

In the past it has been customary for such a third lever i2 to control its own set of contacts as shown in Fig. 3. In Fig. 3 this third lever, designated by the reference character I6, operates a movable contact 68 cooperating with a stationary contact Il. Where direct current is used it is desirable to shui! out the arc between the contacts I8 and il by the use of a permanent magnet l2. Since the third` lever is adjacent to contact Il it is desirable to insulate this lever by means of the insulating strip Il. However, if this strip' should be riveted to the lever li by ordinary rivets, arcing might take place from the rivets. Therefore I employ novel rivets 66 formed' of a plastic electrical insulating material preferably of the thermo-plastic type, such as that known by the name Polystyrene" or that known' by the name Tenite The rivets may be made either solid or hollow. The rivet is set cold and riveted substantially in the manner of an ordinary solid metal rivet. The'head of the'rivet is preferably under-cut onthe face which is positioned against the work or piece held to provide space for a ilowing of the plastic material when the rivet is being riveted. By the use of such rivets and by the use of the insulating strip 64k arcing between the third lever 56 and the nent magnet 62 is effectively prevented.

Instead of operating a set of contacts directly by the third lever 62 in Fig. 1 it is proposed by this invention to operate through the link 18, the

permaautomatic overload contact 12 shownin Fig. 2, .thi slink-1.8 includes an insulating section 14 which prevents the operating mechanism from becoming electrically charged. The starting and overloadl control mechanism is mounted upon a base 16 pf electrical insulating material by means of the screws 18 and spacers 88 surrounding the screws. The current from the electrical supply line 82 connects to a stud 84 fastened to the base 16. The upper portion of this stud 84 carries a stationary contact 86 with which the movable overload contact 12 is adapted to make contact.

- This movable overload contact 12 is mounted sprung upwardly away from the base at the end provided with the notches so that the location of the notches may be adjusted by the adjusting screw 94.

The toggle lever 98'is connected by a tension toggle spring 96 to the overload bimetal 98 which is anchored to the base by the bracket |8|. This bracket l8i, through a plate |83 provided beneath the plate 16, Aelectrically .connects to the contact strip 88. Connected to the bracket |8| is an electric heater |851 which in turn connects to an anchoring post |81. This anchoring post- |81 supports a bottom leg of a U-shaped timing device |89 which carries a contact u'pon the end of its upper leg.

'I'he yoke portion of the bimetal device |89 is connected by the conductor strip I3 to a bracket ||5 which is fastened to the iron frame |,|1 of the electromagnetic starting control. This frame H1 has a portionl extending around the electromagnet H9 for carrying the ilux and increasing the eii'ectiveness of the electromagnet H9. Thel electromagnet ||9iseonnected to the frame ||1 by the conductor |2|. The electromagnet ||9 is also connected by the conductor |23 to a bracket |25 carrying a contact |21 withwhich the contact is adapted to cntact. This bracket |25 is connected to the stud |29 which` in turn is connected by the conductor |3| to the main winding 240i.' the electric motor 22.

The` electromagnet ||9 is provided with an armature i 33 which assumes a full line position when attracd and the dotted line position designated by the reference character I 35 when'it is released. A U-shaped stop |31 of felt or other material limits the movement of the amature |33. The armature |33 is' carried by a thin member |39 ot spring material which is an' chored' by the rivets |4| to a ilange provided on the base 1. This member |39 is provided with a contact-carrying tongueY |43 carrying a contact |45 adapted to make contact with the stationary contact |41 mounted upon a bracket which is fastened to the stud |49. This stud |49 is connected by the conductor |5| to the starting winding 26. The common point between the starting winding 26 .and the running winding 24 is connected to the other source conductor |53.

Withthis arrangement, when the temperature at the thermostat bulb 38 is sulciently low the bellows 42 is collapsed, thereby allowing the primary 1ever 46 to move downwardly in a clockwise direction under the iniiuence of the range spring to operate the snap-acting mechanism and i to lraise the third lever 52.and the link 18 as well as the movable overload contact 12. When the thermostat bulb 38 becomes sumciently warm the primary lever 46 will be moved upwardly by the -bellows 42 to operate the snap-acting mechanism in order to lower the third lever 52 until its stop projection |51 engages the adjacent portion of the frame 44. 'l'his will also lower the link 18 and allow the movable over'load contact to engage the stationary overload contact 86.

This will allow current to iiow from the source conductor 82 through the stud 84, the contacts 86 and 12, and the strip 88 to the bracket |8I. From the. bracket |8| the current traverses the heater element |85, the bimetal |89, the conductor strip I i3, the bracket |I5,` the frame member' H1, the electromagnet H9, the conductor |23, the stud |28 and the conductor |3| to the main winding 24 which connects to the other source conductor |53. This causes the attraction of the armature |33, causing the closing of the starting contacts |45 and |41, allowing current to iiow from the frame lllthrough the arma-A ture support |39, the contact arm |43, the contacts |45 and |41, the stud |48 and the conductor I5! to the starting winding 26 which also connects to the other source conductor .|53.

Under normal voltage conditions, due to the reduction of current ilow through the main winding 24, the electromagnet ||9 will release the armature |33 when the motor approaches a normal running speed to open the starting contacts |45 and |41 to deenergize the starting winding 26. However, if the electromagnet ||9 -should fail to release the armature |33 at the proper time due to unusual 'voltage conditions, the lower leg of the bimetal timer |89 will become heated suillciently to cause the bimetal to bend and to close the contacts |I| and |21 in order to shunt the electromagnet ||9 and thus allow the armature |33 to be released and to deenergize the starting winding 26. Should there be an excessive current iiow through the heater |35' the bimetal 98 will be heated to operate the toggle lever 98 which will raise the hooked end of the contact strip 88 tp separate the contacts 12 and 86 to stop'the operation of the system.

The switch 44 is provided with a temperature adjusting mechanism including an adjusting screw |6| which adjusts the tension of the range spring |55. This screw |6| may be rotated by reciprocable knob member |63 provided with a' groove engaging a bell crank extension |61 of a toggle lever |69 having knife edges received in notches provided in an anchoring member |1|. The toggle lever |69 is connected by a tension toggle spring |13 with an adjustable spring an chorage |15 which may be adjusted by the |33 is pushed inwardly the toggle leverv |33 will be pushed across the dead-center of the toggle' spring |1| to cause the lever |33 to tum about 60 degrees.. This will cause the bell crank eiifllV of the lever to engage thepm'iectingportion4 |13 of the primary lever 43 and push the primary lever 43 downwardly so that it will operate the` snap-acting mechanism to' open the motor circuit. The bell crank extension upon the-release' of the knob member |33 will continue tsibev held which interpose's a addition to that A o |33. 'Ihis will provide a'fsingle cycle-having a temperature suillcientlyf high for Ydeirostirig the evaporator 33.

Itfwill be understood that the bellows 42 and itsoperating mechanismcanbe independently o! the remainder ofthe motor control mechanism through the knob |33. while the operation of the electromagnetmay be controlled independently by the adjusting screw |3| which adjusts the angle oi' the anchorage of the armature supporting member |33. The overload control may be also adjusted independently by the set screw 34 whichadjusts the location of the knife edge support 32 and may be further adjusted by the set screw |33 which limits theopening movement oi the toggle lever 33. g

In Fig. 5 the motor starting control system is simpliiied by combining the timer |33 with the contact arm |43. In Pig. 5 there is shown a motor 232 provided with-a starting winding 234 and a running winding 233. YThe motor receives its energy from a source 233, providing source s '3 mmertneenerginuoneftne cicciona-d2" nam ina- Iiind.however.thatthecontactarm243will valso operate to separate the contacts 234 and 233 against the projection |13 fby togglcsprin1g|13' rango #Prins vconductors 2|3 and 2|2. 'Ihe operation of the motor 232 generally may be controlled by or more switches 2|4, such as the thermal overload and the temperature-responsive bellowsoperated control lor the overload. auch as is shown 'in Pigs. 1, 2 and v4. vThe source conductor 2|2 connects to the frame 213 of soft iron. This frame extends to an elt 2|3 and pro vides an adjustable anchorage223 at its opposite end for the spring hinge member 222 which connects to the amature 224.V Stop members 223 of felt are provided aboveand below the amature 224 for limiting its movement. The angularity of the anchorage 223 for the-spring member`222 is adjustedhytheadjusting screw 228 in order to adiustvthe release of the armature by the eiectromagnet 2|3.

The electromagnet 2|3 has one end connected tothebase 2I3andtheothe`rendconnectedby.

the conductor 233 to one endoithemainwinding 233. The otherendfthstaingwindingu.

is connected by the conductor 232 to a stationary insulated contact 234 providedupon an insulating member 233 resting upon thebase 2|3. this contact 234isadaptedtobecontacted.whenthe armature 224 is attracted, by a movable contact 233 provided upon the end or a contact arm 243.

This contact'arm 243 diners trom the contactv arm |43 principally in that it is rormedoi'a separate piece of bimetal whichis fastenedontop ofthespringmember 222 insteadofbeinganintegral parto! the spring munber 222. This bimetalarm243 maybemadeofsuchasisetliat whenthestartingwindingumsbeenenergised ssumeientpnztnor'umeuieheanngentor lthecurrentilowingtlirougliit'vlillcauseitto ,curiawayiromthceontaet234toseparatethe `oontacts234and233to whenit curls toward the contact 234 when heated by the current. 'Ihis occurs by reasonofthe factthatthiscontactarmincurlingdownward isheldbythestationarycontact234andthe reactiontlnrefmmraisesthearmature224away fromthe 2I3 toa position where the attraction between the amature 224 and the2|3isreducedtosuchanex tentthatthe armature224isreleasedandthe 233 and.234 are separated. A stop maribel 242 k provided at the end of the con tact arm 243 to limit its downward movement. Thus; this bimetal timing. device operates upon ythestartingwindingcurrenttodirectlyseparlte thestartingwindingcontactsinstead of shuntingtheelectaccordingtotheheating eilect oltheentire motor currentas is donein the iirst modiilcation. It willbe seen that this volatileliouidandtbeentiresystemissealedby' the sealing ot the end of the capillary tube.

A thimble 331 extends Within the bellows 33| andlsfastenedtoandsealedtothebaseofthe bellows 33|. This thimble supports an adjusting vscrew333 carryingaspringretainer 3||vfor adjusting the tension ot the compression spring 3|3 which has its upper end bearing against anupper spring retainer 3|3. This spring retainer 3|3 bearsagainsttheends3l`land3|3 ofthebell cranklevers32| and323 whicharepivotedtothe ilange333ofthebase3l3bytheleafspring hinges 323 and 321. The lower ends of each or the toggle levers are provided with toggle blades.- The blade 33| has a. pointed end whichis pivoted Ato theendofthe lever 32| and its oppositeend is plvotally mounted in the operating member 333. l'I'hetogglelilade 333likewisehasa pointed end which is pivotally mounted at the extreme end of the leverr323, while its other end is pivotally molmted in notches provided upon the operating member 333. 'Ihe operating member 333 an adiustable stop screw 331 at its lower end which is supported by the insulating plate 333. It diould be noted that, in its lowermost posion, the operating member 333 does not Acarrythetogalehlades-33l and333 acroastheir dead-center position. The operatingmember 333 isconnectedtothemovableendofthebellowsby spring 34| throughwhichthe operation o! the operating member takes place.

Ihesofardescribedhasno contactin itself, but the starting and overloadcoutactisoperated toopen themotorci'rcuitthroughanoperatingarm343 ftothebottomofthehladelsothat whenthebladeismovedtothepositionshownin Fig.8itwillopenboththestartingandtheover meschers.

'Ihestartingandoverloadconirolincludesan overloadblmetalmemberwsndastartlngbithe starting u' metal member 341. 'mestartingllmetal member 341 is fastened to the contact pin 349 (Fig. 6) which in tu'rn i's connected to the source conductor 35|. The overload blmental member 345 is connected to a conductor 353 which in turn is connected through a conductor 355 to a conductor 351 which in turn connects to a exible conductor 359, (Fig. 8) connecting to the end of the bimetal 341, which is provided with a movable contact 36|. The opening movement of this movable contact 36| is adjusted by a set screw 363 supported by the insulating member 365. Fastened to the end of the bimetal strip 341 and to the conductor strip 359 by the contact 36|, is a U-shaped `spring metal member 361 which has the ends of its legs extending into the notches 369 provided in the insulating spacer member 316. The bimetal strip 341 is kept under tension so as to slightlyy bow the legs of the spring member 361. This provides a snap-acting control for the operation of the bimetal 341. The bimetal'34i is further adjusted by the adjusting screw 313 which extends through the member 365 and bears against the strip 315 which in turn has a hooked end bearing against the bimetal 341 adjacent its anchoring point provided by the contact pin 349. This strip 315 will tend to impose a slight load upon the bimetal in.one direction.

The overload bimetal 345 is likewise provided with a U-shaped spring metal member 311 which is fastened to it by its contact 319 (Fig. 8). This contact 319 is adapted to make engagement with a normally stationary'contact 38| provided at the end of a spring metal member 383 which is biased to rest against the stop screw 385 to adlust the location of the contact 38| in order to adjust the operation of the overload bimetal 346. In addition, the set screw 381, through the yoke 389 which connects to the spring member 390, also tends to deect the bimetal 345 through the hooked end which engages the bimetal 345 adjacent the conductor member 353. The spring member 383, which carries the stationary contact 38| at one end, connects to a conductor pin 393 at its other end'which in turn is connected by the conductor 395 to the main winding 391 of the electric motor 39s. The contact ser is adapted to make engagement with a stationary contact 302 provided upon the end of a spring member 404 which is normally biased to rest against the insulating member 339. This spring member 404 is anchored to the conductor pin 406 which in turn connects to the starting winding 408of the motor 399.

As shown in Fig. 8, when the capillary tube is cooled, the bellows 30| is in a collapsed condition. The lever arms 32| and 323 move, toward each other to raise the operating member 333 and to turn the toggle blade 335 in a clockwise direction to cause the arm 343 to engage the end of the bimetal 345 to separate the overload contacts 319 and 38|. A yoke 4|0 extends from the end of the bimetal 345 to the end of the bimetal 341 so'that the opening of the contacts'319 and 38| will also open the contacts 36| and 302 in order to deenergize the'starting winding.

` conductor through the connector pin m.

When the capillary tube 329 becomes warm the bellows 30| will expand to move the spring 34| and the operating pin 333 downwardly against its stop 331 to move the arm 343 in a counter-clockwise direction away from the end of the overload bimetal 345 to the position shown in Fig. -6. If the bimetals 345 and 341 are cool, as they would be expected to be under normal conditions, current will flow from the source the bimetal 341, thecontacts 36| and 302, and the strip 404 to the connector pin 406 which in turn connects to the starting winding 408. The main winding current also ilows through a portion of this circuit, namely the conductor 35|, the connector pin 349. and the bimetal 341. However, from the contact 36|. the vmain winding current extends through the conductor strip 359 through the conductors 351, 355 and 353 to the anchoring end of the bimetal 345 which carries the current to the contacts 319 and 38| from which point the main winding current ows through the spring member 383 to the connector pin 393 which in turn is connected by the conductor 395 to the main winding 391, which joins with the other end of the starting winding 408 to connect to the other source conductor 929.

After sufficient current has passed through' the bimetal 341 to allow the motor 399 toA start and'to substantially attain full speed,the bimetal 341 will become heated sumciently to overcome the opposition of the bowed legs of the U- shaped spring member 361 to snap the contact f 36| away from the contact 302 to a.l position against the set screw 363 in order to open the starting winding circuit and to deenergize the starting winding 408. For the remainder of the cycle the motor 399 Vwill operate upon the main winding 391 alone. Should there be any overload at any time, the current which passes through. the bimetal 345 will heatthe bimetal 345 sumciently to cause it to snap the contact 319 away from the contact 38| to open the main winding circuit to deenergize the main winding 391. In this opening movement the end of the bimetal 345 will engage the yoke 4|0 to move the starting winding contact 36| to open circuit position'against the set screw 363.A When the capillary tube 329 has been cooled suiliciently the bellows will collapse and move the toggle blades to the position shown in Fig. 8, thereby opening the main winding contacts 319 and 38t as well as the starting winding contacts 36| and 302 said movable contact; and p through the medium of the arm 343 and the yoke M0.

'I'he differential of the main winding contacts is adjusted by the set screw 385 while the differential of the starting winding contacts is adjusted by theset screw 363. The operating range of the main Winding contacts is adjusted by the set screw 381 while the voperating range of the starting winding.contacts is adjusted by the set screw 313. Since the screw 309 lseparately adjusts the operation under the control of the bellows 30|, separate adjustments arethereby provided for each function ofl the control.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within Ithe scope of the claims which follow.k

What is claimed is as follows:

1. In combination, an electric motor having phase and main windings, a current responsive starting control fory controlling the energization of the phase winding, overload control contacts including a single movable contact and a xed contact for controlling the energization of at `least the running overload control means for operating to open and closed positions -operated means for operating said movablecontact, a rst `snap-,acting means for I: :ontrolli-rig.,thegoperation of said movable contact; and Aagssfectind snap-act,

ing means for controlling the operation of the pressure-operated means.

2. A control including a pressure operable diaphragm means, a control device to be operated from one position to another and return, a toggle means constituting at all times'the major control of the movement of the diaphragm means, means for preventing the movement of the toggle means across dead center position, and means operated by the diaphragm means for operating said control device from one position to another.

3. A control including a pressure operable diaphragm means, a control device to be operated from one position to another and return, a toggle means constituting at all times the major control of the movement of lthe diaphragm means, means for preventing the movement of the toggle means across dead center position, and a lost motion means operated by said diaphragm means ior operating said control device.

4. A control including a pressure operated diaphragm means, a set of rigid toggle members constituting the major force opposing the movevment of the diaphragm means, spring means exerting a force upon the toggle members, means for limiting the ovement of the toggle members to one side of t e dead center position and for stopping the movement a short distance prior to leaching the actual dead center position, and a control device operated by the movement of the diaphragm means.

5. In combination, an electric motor having main and phase windings. a starting control for controlling the energization of the phase winding, an actuating element for said starting control, a self-resetting overload protector including means for deenergizing at least the running winding, means including a mechanical transmitting element for mechanically opening said starting control upon the opening of the overload protecior, a second actuating element responsive at least to the current flowing through the running winding for operating said overload protector, and separate adjusting means for said protector and said starting control.

6. In combination, an electric motor having main and phase windings, a starting control for controlling the energization of the phase winding, an actuating element for said starting control, a self-resetting overload protector including means for deenergizing at least the running Winding, means including a mechanical transmitting element for mechanicallyopening said starting control upon the opening of the overload protector, a second actuating element responsive at least to the current flowing through the running winding for operating said overload protector,

l separate adjusting means for said protector and and said starting control to said starting control, and a fluid motor for mechanically moving both said overload protector open circuit position. ALBERT O. GROOMS. 

